OS039-07
Observing rain layers, diurnal warm layers, and their impacts in tropical oceans

Monday, 14 December 2020: 10:18
Virtual
Elizabeth Jennifer Thompson1, Jim Moum2, Chris W Fairall3, Kyla Drushka4, Steven A Rutledge5, Suneil Iyer6, Andrey Shcherbina7, Luc Rainville6, Nan-hsun Chi6, Andy T Jessup8, Eric A D'Asaro9, Carol Anne Clayson10, James B Edson11, Janice L Bytheway12, Haonan Chen13 and Jie Yang14, (1)NOAA PSL, Physical Sciences Lab, Boulder, CO, United States, (2)Oregon State University, College of Earth Ocean & Atmospheric Sciences, Corvalis, OR, United States, (3)NOAA Boulder, Boulder, CO, United States, (4)University of Washington, Applied Physics Laboratory, Seattle, WA, United States, (5)Colorado State University, Department of Atmospheric Science, Fort Collins, CO, United States, (6)Applied Physics Laboratory University of Washington, Seattle, WA, United States, (7)Applied Physics Laboratory University of Washington, Kenmore, WA, United States, (8)Applied Physics Laboratory, University of Washington, Seattle, WA, United States, (9)Applied Physics Lab, Univ of Washington, Seattle, WA, United States, (10)Woods Hole Oceanographic Institution, Physical Oceanography, Woods Hole, MA, United States, (11)Woods Hole Oceanographic Institution, Woods Hole, MA, United States, (12)Cooperative Institute for Research in Environmental Sciences, Boulder, CO, United States, (13)Colorado State University and NOAA Physical Sciences Laboratory, Boulder, CO, United States, (14)Applied Physics Laboratory, University of Washington, Acoustics, Seattle, WA, United States
Abstract:
Near surface stratification of the ocean by rain and solar radiation absorption limits the depth penetration of ocean mixing and amplifies the surface variability of ocean temperature, salinity, and air-sea fluxes. We review investigations of these coupled processes from recent field campaigns across the tropical Indian and Pacific Oceans: PISTON 2018-2019, SPURS-2 2016-2017, DYNAMO 2011. When diurnal warm layers are present, the diurnal variations in latent, sensible, and buoyancy fluxes into the atmosphere are amplified due to warm SST and atmospheric boundary layer drying. When stable "rain layers" exist at the surface following precipitation, air-sea fluxes are also enhanced by rain-cooled SST because the atmospheric boundary layer cools considerably more than the ocean during rain and also often dries. We discuss in-situ, radar-, and satellite-based strategies for measuring rain layers, diurnal warm layers, and their impacts on the upper ocean and lower atmosphere. Using only the surface wind speed, surface buoyancy flux, and Monin-Obukhov similarity theory we derived estimates of ocean stable layer depth and the maximum surface wind speed for which ocean stratification should persist for a given surface buoyancy flux. During the equatorial DYNAMO experiment, these estimates accurately diagnosed 36 out of 44 observed stratification events (88% success rate) and also accurately diagnosed the wind limits of these events. We assess the performance of these techniques during off-equatorial field campaigns: SPURS-2 and PISTON. The success of this stable layer detection method suggests a means to determine the presence of stable near-surface rain layers and diurnal warm layers in the ocean from only surface measurements in the atmosphere: wind, rain rate, and air-sea heat fluxes.
<< Previous Abstract | Next Abstract >>